Add document provider integration

README.md

@@ -58,6 +58,25 @@ end
 Worst case, you'll need to copy the code from the current `pipeline` target
 and add a call to `Opencensus.Absinthe.add_phases/1` as above.
 
+If you are using `DocumentProvider` modules, you will need to integrate into
+their `pipeline/1` callback as well. If your `DocumentProvider` modules do not
+yet override this callback, then this is fairly straightforward:
+
+```elixir
+def pipeline(%{pipeline: as_configured}) do
+  as_configured
+  |> Absinthe.Pipeline.from(__absinthe_plug_doc__(:remaining_pipeline))
+  |> Opencensus.Absinthe.add_schema_phases()
+end
+```
+
+If you already override the `pipeline/1` callback, just append this to the end:
+
+```elixir
+# ... result
+|> Opencensus.Absinthe.add_schema_phases()
+```
+
 ### Middleware
 
 Your [middleware callback][c:middleware/3] needs to run its output through

lib/opencensus/absinthe.ex

@@ -41,6 +41,25 @@ defmodule Opencensus.Absinthe do
 
   Worst case, you'll need to copy the code from the current `pipeline` target and add a call to
   `Opencensus.Absinthe.add_phases/1` as above.
+
+  If you are using `DocumentProvider` modules, you will need to integrate into
+  their `pipeline/1` callback as well. If your `DocumentProvider` modules do not
+  yet override this callback, then this is fairly straightforward:
+
+  ```elixir
+  def pipeline(%{pipeline: as_configured}) do
+    as_configured
+    |> Absinthe.Pipeline.from(__absinthe_plug_doc__(:remaining_pipeline))
+    |> Opencensus.Absinthe.add_schema_phases()
+  end
+  ```
+
+  If you already override the `pipeline/1` callback, just append this to the end:
+
+  ```elixir
+  # ... result
+  |> Opencensus.Absinthe.add_schema_phases()
+  ```
   """
 
   alias Absinthe.Middleware
@@ -68,6 +87,28 @@ defmodule Opencensus.Absinthe do
     )
   end
 
+  @doc """
+  Add tracing phases to an existing pipeline for schema.
+
+  ```elixir
+  pipeline =
+    Absinthe.Pipeline.for_document(schema, pipeline_opts)
+    |> Opencensus.Absinthe.add_schema_phases()
+  ```
+  """
+  @spec add_schema_phases(Absinthe.Pipeline.t()) :: Absinthe.Pipeline.t()
+  def add_schema_phases(pipeline) do
+    pipeline
+    |> Absinthe.Pipeline.insert_after(
+      Absinthe.Phase.Schema,
+      Opencensus.Absinthe.Phase.SchemaPush
+    )
+    |> Absinthe.Pipeline.insert_after(
+      Absinthe.Phase.Document.Result,
+      Opencensus.Absinthe.Phase.Pop
+    )
+  end
+
   @doc """
   Add tracing middleware for field resolution.
 

lib/opencensus/absinthe/middleware.ex

@@ -12,15 +12,20 @@ defmodule Opencensus.Absinthe.Middleware do
   @impl true
   @spec call(Resolution.t(), term()) :: Resolution.t()
   def call(%Resolution{state: :unresolved} = resolution, field: field) do
-    acc = Acc.get(resolution)
+    case Acc.get(resolution) do
+      # nil ->
+      #   Logger.error("Handling a field resolution with no span metadata: #{inspect(field, pretty: true)}")
+      #   resolution
 
-    span_options = %{
-      attributes: field |> extract_metadata() |> Enum.into(%{}, &stringify_keys/1)
-    }
+      acc ->
+        span_options = %{
+          attributes: field |> extract_metadata() |> Enum.into(%{}, &stringify_keys/1)
+        }
 
-    span_ctx = :oc_trace.start_span(field |> repr(), acc.span_ctx, span_options)
-    middleware = resolution.middleware ++ [{{__MODULE__, :on_complete}, span_ctx: span_ctx}]
-    %{resolution | middleware: middleware}
+        span_ctx = :oc_trace.start_span(field |> repr(), acc.span_ctx, span_options)
+        middleware = resolution.middleware ++ [{{__MODULE__, :on_complete}, span_ctx: span_ctx}]
+        %{resolution | middleware: middleware}
+    end
   end
 
   @doc false

lib/opencensus/absinthe/phase/push.ex

@@ -9,8 +9,9 @@ defmodule Opencensus.Absinthe.Phase.Push do
 
   @impl true
   @spec run(Blueprint.t(), keyword()) :: Phase.result_t()
-  def run(blueprint, _opts \\ []) do
-    parent_span_ctx = :ocp.with_child_span("Blueprint")
+  def run(blueprint, opts \\ []) do
+    child_span = Keyword.get(opts, :child_span, "Blueprint")
+    parent_span_ctx = :ocp.with_child_span(child_span)
     span_ctx = :ocp.current_span_ctx()
 
     acc = %Acc{

lib/opencensus/absinthe/phase/schema_push.ex

@@ -0,0 +1,15 @@
+defmodule Opencensus.Absinthe.Phase.SchemaPush do
+  @moduledoc false
+
+  use Absinthe.Phase
+
+  alias Absinthe.Blueprint
+  alias Absinthe.Phase
+
+  @impl true
+  @spec run(Blueprint.t(), keyword()) :: Phase.result_t()
+  def run(blueprint, opts \\ []) do
+    opts = Keyword.put_new(opts, :child_span, "Blueprint")
+    Opencensus.Absinthe.Phase.Push.run(blueprint, opts)
+  end
+end